In conventional tank-type vacuum circuit breakers, there is a well-known vacuum circuit breaker that is configured in such a way that a main body of the vacuum circuit breaker is installed in a pressure tank in which an insulation medium, such as SF6 gas or dry air, is encapsulated at about 0.05 to 0.5 MPa·g of gas pressure, and the main body of the vacuum circuit breaker is led to the outside of the pressure tank and connected to a main circuit conductor.
A conventional tank-type vacuum circuit breaker is illustrated in FIG. 6. Two bushings 32 and 33 are individually arranged for each phase on an upper position of a tank 31 having a cylindrical shape, which is arranged in a state where an axis line of the tank is extended in a horizontal direction, and a main body 34 of the vacuum circuit breaker is horizontally arranged in the tank 31. Moreover, a fixed side 35 of the main body 34 of the vacuum circuit breaker is connected to the bushing 32, which is one side of the bushings, and a movable side 36 of the main body 34 is connected to the bushing 33, which is other side of the bushings. Furthermore, the main body 34 of the vacuum circuit breaker is insulated and supported, via supporting insulators, at both end portions in an axis direction of the tank 31. The movable side 36 is led from one end portion of the tank 31 by an insulation rod 37 and connected, via an operation rod 38, to a shaft 39 that can be rotated to a lower side, and moreover, the shaft 39 is configured in such a way that the shaft 39 is linked to an operation mechanism by a three-phase-link bar that is not illustrated (for example, refer to Patent Document 1).